/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.api.extend;

import axil.api.AxilObject;


/**
 * An object representing the values passed to a function or operator when it
 * is being invoked. If the function is marked for lazy evaluation, then the
 * parameter values need to be evaluated before being used. For eager evaluation
 * (which is the vast majority of functions), then the values passed are ready
 * to use.
 * <p/>
 * This interface is not intended to be implemented by host applications. This
 * interface provides a mechanism for encapsulating the implementation. Use the
 * Axil.instance() object to access instances of this object.
 */
public interface Parameters {
	/**
	 * Get the first parameter to this function. The value returned is never
	 * null, but may be the special Axil nil object.
	 */
	public AxilObject a();

	/**
	 * Get the second parameter to this function. The value returned is never
	 * null, but may be the special Axil nil object.
	 */
	public AxilObject b();

	/**
	 * Get the third parameter to this function. The value returned is never
	 * null, but may be the special Axil nil object.
	 */
	public AxilObject c();

	/**
	 * Get the actual number of parameters passed. The value returned is always
	 * greater than or equal to zero. This is used when dealing with an arbitrary
	 * number of arguments to a function.
	 */
	public int size();

	/**
	 * Get a parameter from the set passed to this function for execution.
	 * The first parameter is in slot zero. The value returned is never
	 * null, but may be the special Axil nil object. Use the size() method when
	 * dealing with an arbitrary number of arguments.
	 */
	public AxilObject at(int index);
}
